It is often desirable when air-conditioning the interior of a vehicle to be able to set different temperatures for two or more zones in the vehicle, e.g. right/left and/or front/rear, since the passengers may have differing views concerning a comfortable temperature and, e.g. because the sun may heat different parts of the interior to a differing extent. This is particularly important in hot weather when air flowing into the vehicle need not be heated, but rather cooled. The temperature subjectively experienced by a passenger is dependent not only on the actual temperature of the air, but also on its quantity, rate of flow and humidity.
Thus, besides affecting the actual temperature of the air, the subjective temperature can be altered by altering the air velocity. Increased air velocity gives a sense of lower temperature. Individual subjective temperature can be obtained even if the temperature of the air is the same, by arranging a separate fan to the exhaust opening in each zone, each fan being individually regulated.
Besides arranging separate fans, separate heat exchangers may also be arranged for factual heating and cooling of the air temperature to the different zones. However, this generally entails complicated and bulky air-conditioning systems which are not easily fitted into the limited space available in ordinary private vehicle. They are also extremely expensive solutions. Common to the above-mentioned solutions is that they require a considerable amount of space, and are complicated and expensive.